SOx control compositions

ABSTRACT

A composition comprising a coprecipitated magnesia-lanthana-alumina (MgO-La2O3-Al2O3) wherein the MgO component is present as microcrystalline phase, having a BET (N2) surface area of at least 130 m2/g, preferably combined with a catalytic oxidation and/or reducing promoter metal such as ceria, vanadia and/or titania.

The present invention relates to compositions which are used to controlsulfur oxide (Sox) emissions from fluid catalytic cracking (FCC)operations, and more particularly to SOx gettering compositions that arecapable of capturing Sox during the oxidative regeneration of FCCcatalysts, and releasing sulfur as H₂ S in the reducing atmosphere ofthe catalytic cracking reaction zone.

Compositions which have been used to control SOx emissions typicallycomprise magnesia, alumina and rare earth oxides.

In particular, U.S. Pat. No. 4,472,267, U.S. Pat. No. 4,495,304 and U.S.Pat. No. 4,495,305 disclose SOx control compositions which containmagnesia-alumina spinel supports in combination with rare-earths such asceria and lanthana, and U.S. Pat. No. 4,836,993 discloses thepreparation of magnesium aluminate (MgAl₂ O₄) and magnesia-aluminacomposites that are combined with a rare earth and used as sulfur oxideabsorbent in FCC processes.

While prior compositions have been successfully used to control the SOxemissions from FCC units, the industry requires compositions that areefficient for both the pick-up of SOx in the catalyst composition duringregeneration, and the release as H₂ S in the cracking reaction.

In addition, SOx control agents which are used in the form of separateparticulate additives must have hardness and attrition properties thatenable the additive to remain in a circulating FCC catalyst inventory.

It is, therefore, an object of the present invention to provide novelSOx gettering agent compositions.

It is another object to provide SOx control additives for use in FCCprocesses that are efficient for SOx pick-up and release.

It is a further object to provide magnesialanthana-alumina containingSOx control additives that are resistant to attrition and capable ofmaintaining sufficiently high surface area when used in the highlyabrasive and hydrothermal conditions encountered in a commercial FCCprocess.

It is yet another object to provide efficient/economical methods forpreparing SOx control additives on a commercial scale.

These and still further objects will become readily apparent to oneskilled-in-the-art from the following detailed description, specificexamples, and drawing wherein FIGS. 1 and 2 are block diagrams whichillustrate preferred methods of preparing the novel compositions of thepresent invention.

Broadly, my invention contemplates a novel non-spinel, ternary oxidebase having the formula (expressed in weight percent calculated as theoxides):

30 to 50 MgO/5 to 30 La₂ O₃ /30 to 50 Al₂ O₃ wherein the MgO componentis present as a microcrystalline phase.

More specifically, my invention comprises a novel MgO/La₂ O₃ /Al₂ O₃ternary oxide base in combination with catalytically active amounts ofingredients for promoting SO₂ oxidation and/or SO₃ reduction (promotermetals), such as ceria and/or vanadia, which is particularly effectivefor the control of SOx emissions.

The preferred compositions are further characterized by: A fresh surfacearea of 100 to 300 m² /g following 2-hour air calcination at 538° C.,and preferably 130 to 260 m² /g as determined by the B.E.T. method usingnitrogen; a surface area of 100 to 200 m² /g upon 48-hour steaming with20% steam/80% air; a pore volume of 0.4 to 1.0 cc/g as determined bywater; an attrition resistance of 0 to 45 Davison Index (DI) asdetermined by the method disclosed in U.S. Pat. Nos. 3,650,988 and4,247,420 for fresh material after 2-hour air calcination at 538° C.; amicrocrystalline MgO component before and after steaming as determinedby X-ray diffraction; a total promoter metal content of 1 to 15%, andpreferably 2 to 10% by weight ceria and/or vanadia; and a sodium contentof less than about 1% by weight Na₂ O, and preferably less than 0.5 byweight Na₂ O.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1 and 2 illustrate schematic flow diagrams of the multi-stepprocess for preparing the novel coprecipitated compositions.

Referring to FIG. 1, it is seen that the composition may be prepared bya multi-step process described as follows:

(1) A solution containing a lanthanum salt such as lanthanum nitrate isreacted with a solution of sodium aluminate under conditions wherein aseparate stream of lanthanum nitrate is combined with a stream of sodiumaluminate solution over a period of 20 to 60 minutes in a stirredreaction vessel to form a lanthanum-aluminum hydrous oxidecoprecipitate.

(2) The coprecipitated lanthanum-aluminum hydrous oxide slurry mixtureof step (1) is aged at a pH of 9.3 to 9.7 for a period of 0.1 to 2 hoursat a temperature of 20° to 65° C.

(3) The aged slurry of step (2) is then reacted with an aqueous solutionof magnesium nitrate and a solution of sodium hydroxide which are addedas separate streams over a period of 20 to 60 minutes to a stirredreaction vessel at a pH of about 9.5 and at a temperature of 20° to 65°C. to obtain a ternary magnesium/lanthanum/aluminum hydrous oxideprecipitate.

(4) The ternary oxide precipitate of step (3) is separated byfiltration, washed with water to remove extraneous salts, preferablyspray dried, and calcined at a temperature of 450° to 732° C. to obtaina ternary oxide base composition that is free of MgAl₂ O₄ spinel andhaving a surface area of 130 to 260 m² /g.

(5) The ternary oxide base obtained in step (4) is preferablyimpregnated with solutions of cerium and/or vanadium and optionallytitanium to impart a ceria content of about 5 to 15 weight percent and avanadia content of about 1 to 10 weight percent and optionally a titaniacontent of 0 to 10 weight percent.

(6) The impregnated base of step (5) is then dried and calcined at atemperature of 450° to 700° C.

Alternative methods for preparing the novel compositions are outlined inFIG. 2 wherein: the lanthanum/rare earth nitrate, sodium hydroxide,sodium aluminate solutions described above are combined in a mixer(typically a four-port mix-pump) to form a Mg-La/RE-Al ternary hydrousoxide coprecipitate which is aged for about 10 to 60 minutes and thenfurther processed into particulate SOx control additives as shown inalternative processing methods (A) and (B).

The preferred compositions of the present invention are prepared in theform of microspheres which have a particle size range of 20 to 200microns and a Davison attrition index (DI) of 0 to 45, preferably 0 to15, and are suitable for use as SOx control additive in FCC processes.

The SOx control additive composition may be combined with standard,commercially available zeolite-containing FCC catalyst such as theOctacat, XP, Super-D, and DA grades produced and sold by the DavisonChemical Division of W. R. Grace & Co.-Conn.

It is contemplated that the SOx control additive composition may also beincorporated in FCC catalyst particles during manufacture in a catalystpreparation procedure such as disclosed in U.S. Pat. No. 3,957,689, U.S.Pat. No. 4,499,197, U.S. Pat. No. 4,542,118 and U.S. Pat. No. 4,458,623and Canadian 967,136.

The SOx control additive compositions are typically added to a FCCcatalyst in amounts ranging from 0.2 to 2 weight percent and morepreferably 0.5 to 1 weight percent. In one preferred embodiment, the FCCcatalyst will also contain a noble metal combustion/oxidation catalystsuch as Pt and/or Pd in amounts of 0.1 to 10 ppm. The FCC catalyst/SOxcontrol composition mixture is reacted with hydrocarbon gas-oil andresidual feedstocks that contain as much as 2.5 weight percent sulfur(S), at temperatures of 520° to 1100° C. (cracking reaction) and 700° to750° C. (regeneration). In typical commercial FCC operations it isanticipated that the stack-gas SOx emission may be reduced to a level ofabout 50 to 100 ppm SOx.

It is also contemplated that the novel compositions of the presentinvention are useful as supports for hydroprocessing catalysts and asFCC catalyst additives for the passivation of metal such as nickeland/or vanadium.

Having described the basic aspects of my invention, the followingexamples are included to illustrate specific embodiments.

EXAMPLE 1

Two streams, one with 450 ml of magnesium nitrate solution which wasprepared by diluting 411.64 g of Solution A (containing 0.0979 g of MgOin the form of nitrate per gram of solution) with DI-water, the otherwith 507.63 g of 16 weight percent sodium hydroxide solution, weresimultaneously run at approximately the same fractional rate into astirred tank with approximately 300 ml of DI-water. The resulting slurryhad a pH of 12.24. After one-hour aging with agitation at roomtemperature, the fine precipitate was separated from the supernatentsolution by centrifugation. The material was then rinsed twice withhigh-ph (pH adjusted to 10+ using an ammonium hydroxide solution)DI-water and centrifuged, reslurried, twice rinsed and centrifuged againbefore oven drying at 115° C. After 2-hour air calcination at 538° C.,the material was crushed to obtain below 125 micron particles. Theresulting material, hereafter to be referred to as 1A, was found toconsist of 97.33% MgO and 2.34% Na₂ O by weight. BET (N₂) surface areaof 1A was 17 m² /g. A 10.12 g (10.00 g on a dry basis) portion of 1A wasimpregnaed to incipient wetness with 3.3 ml of cerous nitrate solutionbearing 1.11 g of CeO₂. It was dried overnight at 115° C. and then aircalcined at 538° C. for one hour. The resulting material is hereafterreferred to as 1B.

EXAMPLE 2

Two streams, one with 400 ml of magnesium nitrate solution which wasprepared by diluting 306.96 g of Solution A with DI-water, the otherwith 400 ml of sodium aluminate solution which was prepared by combining201.06 g of Solution B (bearing 0.1987 g of Al₂ O₃ per gram of solution)with 60 g of 16 weight percent sodium hydroxide solution, followed bydilution, were run simultaneously at the same rate into a stirred tankwith approximately 300 ml of DI-water. The slurry at the end of run-offhad a pH of 11.32. After 3-hour aging with agitation, pH of the slurrywas lowered to 9.80 using straight nitric acid. The slurry was vacuumfiltered. The filtercake was then twice rinsed with 600 ml of DI-water(pH adjusted to 9.5 with ammonium hydroxide), reslurried in one liter ofDI water (pH adjusted to 9.5) for 5 minutes, filtered again, twicerinsed again with 600 ml of DI-water (9.5 pH) before oven dryingovernight at 115° C. The cake was gently crushed, calcined in flowingair for 2 hours at 677° C., and further crushed to obtain -120 meshparticles. The resulting material, to be hereafter referred to as 2A,had the following composition (weight percent):41.10% MgO, 58.72% Al₂O₃, 0.03% Na₂ O, 0.06% SO₄. This material, like the one described inU.S. Pat. No. 4,469,589, exhibited an X-ray diffraction patterncharacteristic of magnesium aluminate spinel, and had a BET (N₂) surfacearea of 141 m² /g. A 30.27 g portion of 2A was impregnated to incipientwetness with 14.5 ml of cerous nitrate solution bearing 4.48 g of CeO₂,dried overnight at 115° C., and air calcined at 538° C. for one hour. A15.30 g portion of the resulting material,, 2B, was impregnated toincipient wetness with 6 ml of vanadyl oxalate solution bearing 0.385 gof V₂ O₅, dried overnight at 115° C., and air calcined at 538° C. forone hour. The resulting material is referred to as 2C hereafter.

EXAMPLE 3

In order to prepare a ternary oxide base consisting of MgO-La₂ O₃ -Al₂O₃, a staged coprecipitation was carried out as follows: Two streams,one with 400 ml of solution containing 21 g of La₂ O₃ as nitrate and 70g of concentrated (70% HNO₃) nitric acid, the other with 400 ml ofsodium aluminate solution bearing 37.80 g of Al₂ O₃, were runsimultaneously at the same volumetric rate, approximately 80 ml/min.,into a stirred beaker with approximately 300 ml of DI-water. The slurryat the end of this run-off showed a pH of 9.12, and then 9.58 uponone-hour aging at room temperature. To this slurry were added againsimultaneously another two streams at approximately 80 ml/min., one with400 ml of solution containing 471.91 g of Solution A, the other 400 mlof solution containing 460 g of 16 wt.% sodium hydroxide solution. Theresulting slurry having a pH of 10.40 was vacuum filtered, rinsed twicewith 600 ml of high-ph (10-11 using ammonium hydroxide) DI-water,reslurried in 1000 ml of high-ph DI-water, filtered, rinsed twice againwith high-ph DI-water, and filtered. The resulting filtercake was driedovernight at 115° C., crushed and sifted to obtain below 180-micronparticles. A portion of this material air-calcined at 677° C. for 2hours, hereafter to be referred to as 3A, had a BET (N₂) surface area of165 m² /g, and had the following composition (weight percent): 42.63%MgO, 19.10% La₂ O₃, 36.89% Al₂ O₃, 0.09% Na₂ O, 0.18% SO₄. Unlike thebinary base of 2A, 3A showed no MgAl₂ O₄ spinel pattern when examined byX-ray diffraction. Another portion air-calcined at 732° C. for 2 hours,hereafter to be referred to as 3B, had a surface area of 140 m₂ /g. Like3A, the X-ray diffraction pattern of 3B did not show the presence ofMgAl₂ O₄ spinel.

A 45.21 g (45.00 g on a dry basis) portion of 3A was impregnated toincipient wetness with 43 ml of cerous nitrate solution bearing 6.72 gof CeO₂, dried overnight in oven at 115° C., air-calcined at 538° C. forone hour. A 45.78 g (45.00 g on a dry basis) portion of theabove-resulting material was once again impregnated to incipient wetnesswith 21 ml of vanadyl oxalate solution bearing 1.15 g of V₂ O₅, driedovernight at 115° C., and air-calcined at 538° C. for one hour. Theresulting catalyst is hereafter referred to as 3C.

A 30.99 g (30.00 g on a dry basis) portion of 3B was also treatedsuccessively with cerous nitrate solution and vanadyl oxalate solutionin exactly the same manner as in the preparation of 3C to obtain acatalyst having virtually identical chemical composition to 3C. Theresulting catalyst is hereafter referred to as 3D.

EXAMPLE 4

Another ternary oxide base bearing the same three-metal oxides as inExample 3, but in a substantially different ratio, was prepared usingthe procedure described in Example 3 as follows:

The first stage run-off was carried out using two streams, one with 400ml of solution containing 12.60 g of La₂ O₃ as nitrate and 110 g ofconcentrated nitric acid, the other with 400 ml of sodium aluminatesolution bearing 47.27 g of Al₂ O₃. The slurry had a pH of 8.3 when therun-off was completed, showing gradually increased pH to 8.9 upon onehour aging at room temperature. The second stage run-off involved twostreams fed into the above-resulting slurry, one with 450 ml of solutioncontaining 461.18 g of Solution A, the other with 450 ml of solutioncontaining 526 g of 16% sodium hydroxide solution. The resulting slurryhaving a pH of 11.6 was quickly filtered, and treated in exactly thesame manner as in Example 3. A portion of dried and crushed particles ofbelow 180 microns showed a surface area of 221 m² /g upon 2 hour-677° C.air calcination. This calcined material, hereafter to be referred to as4A, had the following composition (weight percent): 43.90 % MgO, 11.75%La₂ O₃, 43.59% Al₂ O₃, 0.09% Na₂ O, 0.08 SO₄. Another portion of driedand crushed particles was air calcined at 732° C. for 2 hours. Theresulting material, hereafter to be referred to as 4B, had a surfacearea of 163 m² /g. X-ray diffraction scan showed that both 4A and 4B hadno MgAl₂ O₄ spinel.

Two ceria-vanadia-promoted catalysts were prepared, one each from 4A and4B in exactly the same manner as in Example 3 as follows: A 39.14 9(39.00 g on a dry basis) of 4A was impregnated with 29 ml of cerousnitrate solution bearing 5.83 g of CeO₂, dried and air calcined. A 40.53g (40 g on a dry basis) portion of the above-resulting material was thenimpregnated with 18 ml of vanadyl oxalate solution bearing 1.03 g of V₂O₅, dried and calcined. The resulting material is hereafter referred toas 4C. A 35.35 g (35.00 g on a dry basis) portion of 4B was impregnatedwith 24 ml of cerous nitrate solution bearing 5.23 g of CeO₂, dried andcalcined. A 35.64 g (35.00 g on a dry basis) portion of the resultingmaterial was impregnated again with 16 ml of vanadyl oxalate solutionbearing 0.90 g of V₂ O₅, dried and calcined. The resulting catalyst,hereafter to be referred to as 4D, is virtually identical to 4C inchemical composition.

EXAMPLE 5

Two streams, one with 300 ml of sodium aluminate solution containing151.00 g of solution B which was described in Example 2, the other with300 ml of nitric acid containing 95 g of 70.5 wt. % HNO₃, weresimultaneously run at the same rate into a stirred beaker containingapproximately 200 ml of DI-Water. The resulting PH was 3.86. Uponone-hour aging with agitation, PH rose to 5.36. After the usual vacuumfiltration, rinse, reslurry, and rinse with DI-water, the filtercake wasdried overnight at 115° C., and air calcined at 677° C. for 2 hours. Theresulting material, 5A, showed an X-ray diffraction patterncharacteristic of delta alumina.

EXAMPLE 6

For two reasons, (1) the overwhelming factor controlling the efficiencyof Sox additive is the capacity of the additive for SO₃ capture, and (2)the fact that the deterioration rate of additive efficiency is ratherhigh, the capacity for SO₃ capture was determined for the fresh samplesonly. Each sample was made up of a blend of 9.950 g of steamed (6 hoursin fluidized bed at 760° C. and 5 psig) OCTACAT® and 0.050 g of freshadditive, all on a dry basis. Each sample was charged into an Inconelreactor having an I.D. of 1.04 cm, and was subjected to two-stagetreatments--(1) a 30-min. reduction in flowing (1500 ml total/min.) N₂containing 2 vol. % H₂, and (2) a 30-min. oxidation in flowing (1.5liter total/min.) N₂ containing 4 vol. % O₂ and 0.0900 vol. % SO₂ at677° C. or 732° C. After each treatment, the sample was discharged,homogenized, and the sulfate level was determined on a one-gram portionremoved from the sample. The weight % SO₄ found in each sample--only 0.5wt. % of the sample is a fresh additive--as a result of the oxidationtreatment was taken as a measure of the capacity for SO₃ capture.

The results summarized in Table 1 revealed the following: While the SO₃captured by 1B (ceria-promoted MgO) appears to be fairly high, asindicated by the high wt. % SO₄, it is apparent that only about 30%--theweight % SO₄ found on 1B corresponds to approximately 30% of thetheoretical maximum attainable for this material--of magnesia in theadditive is effective in capturing SO₃. Thus, the data suggest the keyto obtain a high capacity is to achieve a high degree of dispersion ofMgO or Mg atoms.

While the results of weight % SO₄ found on 2A, 2B and 2C are slightlylower than that for 1B primarily because of the lower MgO loading inthis additive, 2B and 2C are much better than 1B in terms ofeffectiveness in contributing to SO₃ capture, amounting to approximately65% of the theoretical maximum.

Of all the samples from Examples 1-5 evaluated by this test, thepromoted ternary oxide of this invention, 3C as well as 4C and 4D, showthe highest capacity for SO₃ capture, amounting to approximately 75% ofthe theoretical maximum. This is clear evidence for the fact that thenon-spinel compositions of Examples 3C, 4C, and 4D can provide a largernumber of traps capable of capturing SO₃ than the spinel composition ofExample 2A, 2B, and 2C. Catalysts prepared by single-stage run-off,e.g., 9A-13A, exhibit further increased capacities for SO₃ capture.Thus, these data show that there is no requirement for MgO and Al₂ O₃ tobe in the form of spinel structure in order for MgO to have a highcapacity for capturing SO₃.

It is also evident from the data on 5A that alumina by itself hasnegligibly low capacity for SO₃ capture.

EXAMPLE 7

A 0.40 g sample of unblended fresh catalyst was placed in a down-flowVycor glass reactor and was exposed to flowing N₂ containing 9.50 vol. %O₂ and 0.6000 vol. % SO₂ at a total flow rate of 126 ml/min. and 732° C.for a period of 3 hours, and cooled in flowing N₂ for discharge.

A 0.10 g portion of the above-treated sample was examined by temperatureprogrammed reduction (TPR)/mass-spectrometer in a ramp-mode at a rate of20° C./min., using propane at 14.2 ml/min. as a reducing agent. Duringthe course of this TPR run, the concentration of H₂ S was determined asa function of temperature by monitoring mass number 34. Theconcentration of SO₂ released was so low in all runs that the SO₂release data (based on mass number 48 for SO fragment) were simplyignored. The release data summarized in Table II--the lower thetemperature for the onset of release or for reaching the peak release,the easier for the captured SO₃ to be released as H₂ S--reveal thefollowing: (1) SO₃ captured by crystalline MgO promoted with 10 wt. %CeO₂ (1B) cannot be readily released at all.

(2) Without vanadium promotion, the SO₃ captured by magnesium aluminatespinel, with ceria promotion alone, appears to be also difficult toreduce. (3) The ternary oxides of this invention, MgO-La₂ O₃ -Al₂ O₃(e.g., 12A) , are just as good as the Mg₂ Al₂ O₄ spinel carrying oneexcess mole of MgO per mole of Al₂ O₃ in release capability when theyare promoted with ceria and vanadia.

EXAMPLE 8

Binary and ternary oxide bases prepared in Examples 2, 3 and 4 weresubjected to 100% steam at 760° C. and 1 atm. for a period of six hours.Catalyst samples of 9A-13A were steamed over a 48-hour period in flowingair (2.8 liters/min.) containing 20 vol. % steam at 704° C. Theresulting materials were characterized by BET (N₂) surface area as wellas by X-ray diffraction. The results presented in Tables I--IIIreveal--(1) The ternary oxide bases of this invention, Mgo-La₂ O₃ -Al₂O₃, are significantly higher in surface area than the binary oxide baseof MgO-Al₂ O₃ under hydrothermal conditions. (2) Spinel structure is notnecessarily a requirement for an SOx additive to be effective in makinga good SOx transfer catalyst.

EXAMPLE 9

A mixed metal oxide base consisting of Mgo, La-rich rare earth oxides,and Al₂ O₃ was obtained by running a single-stage coprecipitation asfollows: Three streams were simultaneously run into 10,000 g of heelwater in a kettle at 65° C. with good agitation. Stream No. 1 contained757.7 g of MgO along with 241.1 g of La-rich rare earth oxide, all inthe form of nitrate in a total volume of 9840 ml. Stream No. 2 was madeup of sodium aluminate solution containing 723.2 g of Al₂ O₃ and 1120 gof 50 wt. % sodium hydroxide solution in a total volume of 9840 ml.While these two streams were run at the same rate of 400 ml/min., thefeed rate of Stream No. 3 with 16 wt. % sodium hydroxide solution wasvaried so as to control pH of the slurry at 9.3-9.4. After 10-minuteaging the slurry under this condition, pH of the slurry was raised to9.8, and then the slurry was immediately vacuum filtered. The filtercakewas rinsed six times with 15 liters of pH 10 DI-water (pH adjusted withammonium hydroxide). The resulting filtercake was homogenized,Drais-milled, and then rehomogenized before feeding into a spray dryer.A portion of the spray-dried material was air calcined 2 hours at 677°C.

A small portion of the above-resulting base weighing 75.34 g (74.00 g ona dry basis) was impregnated to incipient wetness with 71.5 ml of cerousnitrate solution bearing 11.06 g of CeO₂, dried overnight at 115° C. forone hour. An 83.55 g (82.00 g on a dry basis) portion of the resultingmaterial was impregnated to incipient wetness with 51 ml of vanadyloxalate solution bearing 2.10 g of V₂ O₅, dried overnight at 115° C.,and air calcined at 538° C. for one hour. The resulting catalyst,hereafter to be referred to as 9A, showed the following data: Chemicalcomposition (weight percent): 37.4% MgO, 10.3% La₂ O₃, 12.4% CeO₂, 24.2%total rare earth oxide, 0.2% Na₂ O, 2.5% V₂ O₅, and 35.7% Al₂ O₃. SO₃pick-up was 0.38 wt. % SO₄ when a test was conducted at 732° C. for theSO₂ oxidation described in Example 6. A small portion of 9A was examinedby X-ray diffraction before and after a 48-hour exposure to flowing air(2.8 liters/minute) containing 20 vol. % steam at 704° C. Virtually noMgAl₂ O₄ spinel phase was present in the material before and aftersteaming. BET (N₂) surface areas (m² /g) before and after steaming were167 and 114, respectively.

EXAMPLE 10

A single-stage coprecipitation run was carried out in essentially thesame manner as in Example 9, except that the two streams were run at 325ml/min. into heel water at 45°±70° C. A portion of the spray-driedmaterial was air calcined 2 hours at 677° C. A small portion of theresulting material weighing 71.05 g (70.00 g on a dry basis) wasimpregnated to incipient wetness with 67 ml of solution containing both10.29 g of CeO₂ in the form of cerous nitrate and 2.06 g of V₂ O₅ in theform of vanadyl oxalate. The material was oven dried overnight at 115°C., and then air calcined at 538° C. for one hour. The resultingcatalyst, hereafter to be referred to as 10A, had the following data:Chemical composition (weight percent): 37.4% MgO, 10.1% La₂ O₃, 12.7%CeO₂, 24.2% total rare earth oxide, 0.2% Na₂ O, 2.5% V₂ O₅, and 35.8%Al₂ O₃. SO₃ pick-up in a test with SO₂ oxidation at 732° C. described inExample 6 was 0.47 wt. % SO₄ for this catalyst. Catalyst 10A also showedvirtually no spinel before and after 48-hour/ 704° C. steaming describedin Example 8. BET (N₂) surface areas (m² /g) before and after steamingwere 183 and 114, respectively.

EXAMPLE 11

A single-stage coprecipitation run was carried out in exactly the samemanner as in Example 10, except that stream No. I had an additionalingredient, i.e., it contained 624.8 g of MgO, 213.5 g of La-rich rareearth oxide, and 130.8 g of CeO₂, all in the form of nitrate in a totalvolume of 9840 ml. Stream No. 2 had 723.7 g of Al₂ O₃ in the form ofsodium aluminate along with 832 g of 50 wt. % sodium hydroxide solutionin a total volume of 9840 ml. A portion of the spray-dried material wasair calcined 2 hours at 677° C. A small portion of the resultingmaterial weighing 71.32 g (70.00 g on a dry basis) was impregnated toincipient wetness with 40 ml of vanadyl oxalate solution bearing 1.84 gof V₂ O₅, oven dried overnight at 115° C., and then air calcined at 538°C. for one hour. The resulting catalyst, hereafter to be referred to as11A, showed the following data: Chemical composition (weight percent):38.1% MgO, 10.4% La₂ O₃, 6.9% CeO₂, 18.8% total rare earth oxide, 0.2%Na₂ O, 2.7% V₂ O₅, and 40.1% Al₂ O₃. SO₃ pick-up in a test with SO₂oxidation at 732° C. described in Example 6 was 0.36 wt. % SO₄ for thiscatalyst. Virtually no spinel was found in 11A before and after the48-hour/704° C. steaming described in Example 8. BET (N₂) surface areasbefore and after steaming were 142 and 106, respectively.

EXAMPLE 12

Another single-stage coprecipitation run was carried out in a mannersomewhat different from Examples 9-11. Three streams were simultaneouslyrun into a high speed mix-pump reactor with four ports, allowing theviscous product to fall into 4000 g of heel water in a kettle maintainedat 38°-41° C. with good agitation. Stream No. 1 in this run-offcontained 688.8 g of MgO, 223.9 g of La-rich rare earth oxide, and 120.6g of CeO₂, all in the form of nitrate in a total volume of 9840 ml.Stream No. 2 had a sodium aluminate solution bearing 688.8 g of Al₂ O₃along with 480 g of 50 weight percent sodium hydroxide solution in atotal volume of 9840 ml. While these two streams were fed at the samerate of 400 ml/minute, the feed rate of Stream No. 3 with 16 weightpercent sodium hydroxide solution was adjusted so as to control pH ofthe slurry in the kettle at 9.4-9.5. After aging the slurry under thiscondition for 15 minutes and confirming pH was at 9.5 at the end ofaging, the slurry was immediately vacuum filtered. The filtercake waswashed twice with 15 liters of 9.5 pH DI-water (pH adjusted withammonium hydroxide), and then was vacuum filtered. The resultingfiltercake was homogenized in a high-shear mixer, one-pass Drais milled,and then was rehomogenized. Finally, the slurry was spray dried toobtain microspheres. A portion of the spray dried material was aircalcined at 677° C. for 2 hours.

A 70.52 g (70.00 g on a dry basis) portion of the above-resulting basewas sprayed with 58 ml of an ammoniacal vanadium citrate solutionbearing 1.80 g of V₂ O₅ using an atomizer. After allowing theimpregnated material to stand at room temperature for 20 minutes, thematerial was oven dried overnight at 115° C., and then was air calcinedat 538° C. for one hour. The resulting catalyst, hereafter to bereferred to as 12A, was virtually spinal-free before and after48-hour/704° C. steaming (with 20% steam/80% air), and showed anattrition resistance of 45 DI. Chemical composition (weight percent) wasas follows: 36.1% MgO, 11.0% La₂ O₃, 6.5% CeO₂, 18.8% total rare earthoxide, 0.95% Na₂ O, 2.6% V₂ O₅, and 41.4% Al₂ O₃. BET (N₂) surface areasbefore and after the steaming were 175 and 115 m² / g, respectively. SO₃pick-up for this catalyst was 0.47 weight percent SO₄ in the testdescribed in Example 6. Most important of all, this catalyst exhibitedan excellent release pattern as indicated by the low onset temperaturein Table II for H₂ S release in the propane TPR test and a large amountof H₂ S release observed.

EXAMPLE 13

Illustrated in this example is a single-stage coprecipitation runidentical to Example 12, except for the subsequent washing step. Unlikein Example 12, which corresponds to A route in Figure II, the wash stepin this example is included after the unwashed slurry has been spraydried, according to B route. That is, after the identicalcoprecipitation run-off, followed by aging and filtration, thefiltercake was immediately homogenized using a high-shear mixer withoutwashing at all, milled, rehomogenized, and was spray dried.

A 200 g portion of the resulting microspheres was slurried once in 500 gDI-water at room temperature for 3 minutes, and then washed once with500 g of room temperature DI-water, and filtered. After overnight dryingin a 115° C. oven, the material was air calcined at 704° C. for 2 hours.A 70.44 g (70.00 g on a dry basis) portion of the above-calcinedmaterial was sprayed with 49 ml of an ammoniacal vanadium citratesolution bearing 1.80 g of V₂ O₅ in the form of fine mist. After a20-minute soak at room temperature, the material was oven driedovernight at 115° C., and then was one-hour air calcined at 538° C. Theresulting catalyst, hereafter to be referred to as 13A, showed thefollowing data: Chemical composition (weight percent) : 37.5% MgO, 10,9%La₂ O₃, 6.4% CeO₂ 18.7% total rare earth oxide, 0.2% Na₂ O, 2.5% V₂ O₅,and 40.7% Al₂ O₃. BET (N₂) surface areas before and after 48-hour/704°C. steaming (with 20% steam/80% air) were 185 and 120 m₂ /g,respectively. SO₃ pick-up in a test with SO₂ oxidation at 732° C.described in Example 6 was 0.53 weight percent SO₄. This catalyst wasalso virtually spinal-free before and after the steaming, and was foundto be fairly attrition resistant, judging from its fresh DI of 13. Asshown in Table II, this catalyst is also expected to be reasonably goodin release capability, judging from its test data in the propane TPRtest of Example 7.

                  TABLE I                                                         ______________________________________                                                                    SO.sub.2                                                                              SO.sub.3                                                              Oxi-    Pick-up                                             Sample            dation  wt. %                                     Sample    Description       @ °C.                                                                          SO.sub.4                                  ______________________________________                                        Steamed   An FCC Catalyst   677     0.00                                      OCTACAT ®.sup.a                                                           1B        CeO.sub.2 /MgO    732      0.330                                    2A        MgO.MgAl.sub.2 O.sub.4, Spinel                                                                   67      0.295                                    2B        CeO.sub.2 /2A     677      0.280                                    2C        V.sub.2 O.sub.5 /2B                                                                             677      0.279                                    3C        V.sub.2 O.sub.5 /CeO.sub.2 /                                                                    732     0.34                                                MgO--La.sub.2 O.sub.3 --Al.sub.2 O.sub.3                            4C        V.sub.2 O.sub.5 /CeO.sub.2 /                                                                    732     0.34                                                MgO--La.sub.2 O.sub.3 --Al.sub.2 O.sub.3                            4D        V.sub.2 O.sub.5 /CeO.sub.2 /                                                                    732     0.33                                                MgO--La.sub.2 O.sub.3 --Al.sub.2 O.sub.3                            5A        Al.sub.2 O.sub.3  732      0.007                                    9A        V.sub.2 O.sub.5 /CeO.sub.2 /                                                                    732     0.38                                                MgO--(La/RE).sub.2 O.sub.3 --Al.sub.2 O.sub.3                       10A       V.sub.2 O.sub.5 /CeO.sub.2 /                                                                    732     0.47                                                MgO--(La/RE).sub.2 O.sub.3 --Al.sub.2 O.sub.3                       11A       V.sub.2 O.sub.5 /CeO.sub.2 /                                                                    732     0.36                                                MgO--(La/RE).sub.2 O.sub.3 --Al.sub.2 O.sub.3                       12A       V.sub.2 O.sub.5 / 732     0.47                                                MgO--(La/RE).sub.2 O.sub.3 --Al.sub.2 O.sub.3                       ______________________________________                                         .sup.a This steamed FCC catalyst contains virutally no metal oxides that      can contribute to SO.sub.3 capture.                                      

                  TABLE II                                                        ______________________________________                                        H.sub.2 S Release Temperatures (°C.) in Propane - TPR                  Sample                     Onset   Peak Peak                                  ______________________________________                                        1B    CeO.sub.2 /MgO       627     --   736                                   2B    CeO.sub.2 /MgO.MgAl.sub.2 O.sub.4, Spinel                                                          571     --   715                                   2C    V.sub.2 O.sub.5 /2B  476     645  710                                   3C    V.sub.2 O.sub.5 /CeO.sub.2 /MgO--La.sub.2 O.sub.3 --Al.sub.2                  O.sub.3              536     650  722                                   4C    V.sub.2 O.sub.5 /CeO.sub.2 /MgO--La.sub.2 O.sub.3 --Al.sub.2                  O.sub.3              526     647  712                                   4D    V.sub.2 O.sub.5 /CeO.sub.2 /MgO--La.sub.2 O.sub.3 --Al.sub.2                  O.sub.3              497     647  702                                   11A   V.sub.2 O.sub.5 /CeO.sub.2 /                                                                       530     647  715                                         MgO--(La/RE).sub.2 O.sub.3 --Al.sub.2 O.sub.3                           12A   V.sub.2 O.sub.5 /MgO--(La/RE).sub.2 O.sub.3 --Al.sub.2 O.sub.3                                     475     650  --                                    ______________________________________                                    

                  TABLE III                                                       ______________________________________                                        Properties of Steamed SOx Additives on Bases                                            BET (N.sub.2) Surface Area,                                                   m.sup.2 /g    Powder                                                      Steaming  Before    After   X-Ray Diffrac-                              Sample                                                                              Condition Steaming  Steaming                                                                              tion Pattern                                ______________________________________                                        2A    a         141        70     Well-crystallized                                                             MgAl.sub.2 O.sub.4 spinel                                                     and some MgO                                3A    a         165       137     Microcrystalline                                                              MgO                                         4A    a         221       162     Microcrystalline                                                              MgO                                         9A    b         167       114     Microcrystalline                                                              MgO & CeO.sub.2                             10A   b         183       114     Microcrystalline                                                              MgO & CeO.sub.2                             11A   b         142       106     Microcrystalline                                                              MgO & CeO.sub.2                             12A   b         175       115     Microcrystalline                                                              MgO and micro-                                                                crystalline CeO.sub.2                       ______________________________________                                         a. 6 h/760° C. in 100% steam.                                          b. 48 h/704° C. in 20% steam/80% air.                             

I claim:
 1. A coprecipitated ternary oxide composition having theformula:30 to 50 MgO/5 to 30 La₂ O₃ /30 to 50 Al₂ O₃ wherein the amountsof MgO, La₂ O₃ and Al₂ O₃ are expressed as weight percent, and the MgOis present as a microcrystalline component.
 2. The composition of claim1 further characterized by the absence of a spinel phase, a surface areaof 100 m² /g to 300 m² /g, and a Na₂ O content of below about 1% byweight.
 3. The composition of claim 2 wherein the surface area is 130 to200 m² /g.
 4. The composition of claim 2 having a surface area of 100 to150 m² /g after heating to 704° C. for 48 hours in the presence of 20%steam/80% air.
 5. The composition of claim 1 combined with acatalytically active amount of promoters for SO₂ oxidation and/or H₂ Srelease selected from the oxides of Ce, Pr, Ti, Nd and V.
 6. Thecomposition of claim 5, combined with an FCC catalyst.
 7. Thecomposition of claim 6 wherein the FCC catalyst includes an oxidationcatalyst selected from the group consisting of Pt, Pd and mixturesthereof.
 8. A method for preparing the composition of claim 1 whichcomprises reacting solutions of a lanthanum salt, sodium aluminate, amagnesium salt and sodium hydroxide at a pH of 9.3 to 9.7 to obtain amagnesium-lanthanum-aluminum oxide hydrous coprecipitate, aging saidcoprecipitate for 0.2 to 2 hours, and recovering the aged coprecipitate.9. The method of claim 8 wherein the lanthanum salt is a lanthanum richsalt.
 10. The method of claim 8 wherein a cerium salt is added to obtaina magnesium-lanthanum-cerium-aluminum hydrous oxide coprecipitate. 11.The method of claim 8 wherein a vanadium salt is added to obtain amagnesium-lanthanum-cerium-vanadium-aluminum hydrous oxidecoprecipitate.
 12. The method of claim 8 wherein said coprecipitate iswashed to remove extraneous salts, milled, spray dried and calcined. 13.The method of claim 8 wherein said coprecipitate is filtered, spraydried, washed, dried, and calcined.
 14. The method of claim 8, 10, or 11wherein the solutions are reacted simultaneously.
 15. The method ofclaim 8, 10, or 11 wherein the solutions are contacted in a high-speedmix-pump reactor.
 16. The method of claim 8 wherein the lanthanum saltand sodium aluminate solutions are reacted and the resulting hydrousoxide coprecipitate is subsequently reacted with the sodium hydroxideand magnesium salt solutions.
 17. In a method for preparing attritionresistant inorganic oxide particles wherein aqueous solutions ofaluminum and magnesium salts are reacted to form an aqueous slurry ofhydrous oxide coprecipitate, and the coprecipitate is washed to removesoluble salts and spray dried to obtain discrete particles, theimprovement comprising washing the particles subsequent to spray drying.18. The method of claim 17 wherein the aqueous slurry includes ceriaand/or vanadia.
 19. The method of claim 17 wherein the washed particlesare calcined.
 20. The method of claim 19 wherein the calcined particlescontain a magnesium aluminate spinel phase.